Copper-Plating the Throughholes of Printed Circuit Boards and Cards
Original Publication Date: 1984-Oct-01
Included in the Prior Art Database: 2005-Feb-05
A sputter process is described which, by using a frequency in the kHz range, permits the throughhole walls of printed circuit boards to be uniformly coated with a copper seed layer. The printed circuit board is positioned between two copper electrodes having at least the same size as itself. Copper electrode sputtering is effected at a frequency of up to about 50 kHz. Up to that value, the ions are still capable of following the amplitudes of the AC voltage applied. They have sufficient time at each half-wave to effect a complete DC discharge at the respective electrode, so that the copper of the two electrodes is uniformly sputtered. As the copper is sputtered into the throughholes from either side, a very uniform copper layer is sputtered on the hole walls.